This request is for research presently underway - a study of electrogenosis and the ionic basis of electrical activity. The research is designed to increase our understanding of non-nervous tissue capable of spontaneous electrical activity and the accompanying contractions. This spontaneous activity is usually under the control of an endogenous pacemaker and involves myogenic conduction. Because of the relative primitive nature of myogenic conduction systems they are best studied in invertebrates and in embryological vertebrate tissue. With increased knowledge of developing vertebrate tissue or continually growing invertebrate epithelia, we will be able to more thoroughly understand embryonic development in man. Since ions are important in electrogenesis, self-regulation of ionic concentrations in the tissue structure is also being studied. Epithelial tissue are being studied in two systems. Separated hydra epithelial cell layers are being studied to determine which of the two cell layers is responsible for the electrophysiological properties of intact animals; and transport across flattened tissue sheets of hydra are being studied. Electrical activity across the noninnervated skin of Xenopus embryos which is related to the development of muscular activity is also being studied.